Development ofPhasmarhabditis hermaphrodita(and members of thePhasmarhabditisgenus) as new genetic model nematodes to study the genetic basis of parasitism

Abstract

AbstractThe genetic mechanisms of how free-living nematodes evolved into parasites are unknown. Current genetic model nematodes (e.g.Caenorhabditis elegans) are not well suited to provide the answer, and mammalian parasites are expensive and logistically difficult to maintain. Here we propose the terrestrial gastropod parasitePhasmarhabditis hermaphroditaas a new alternative to study the evolution of parasitism, and outline the methodology of how to keepP. hermaphroditain the lab for genetic experiments. We show thatP. hermaphrodita(and several otherPhasmarhabditisspecies) are easy to isolate and identify from slugs and snails from around the UK. We outline how to make isogenic lines using ‘semi-natural’ conditions to reduce in-lab evolution, and how to optimize growth using nematode growth media (NGM) agar and naturally isolated bacteria. We show thatP. hermaphroditais amenable to forward genetics and thatuncandsmamutants can be generated using formaldehyde mutagenesis. We also detail the procedures needed to carry out genetic crosses. Furthermore, we show natural variation within ourPhasmarhabditiscollection, with isolates displaying differences in survival when exposed to high temperatures and pH, which facilitates micro and macro evolutionary studies. In summary, we believe that this genetically amenable parasite that shares many attributes withC. elegansas well as being in Clade 5, which contains many animal, plant and arthropod parasites, could be an excellent model to understand the genetic basis of parasitism in the Nematoda.